1. Field of the Invention
The invention relates to a blur detection method of images, a monitoring device, and a monitoring system, and more particularly, to a method, a monitoring device, and a monitoring system that can determining whether an image is blurred according to the proportion of blur changes in an originally in-focus area of the image and carry out follow-up specific action.
2. Description of the Prior Art
As an effective image acquiring tool of a monitored scene, a monitoring device or a monitoring system is equipped with camera with the ability of auto-focus, panning, tilting, and zooming, so that clear images from some specific spots or the entire monitored scene may be obtained when the camera is correctly auto-focused.
Most monitoring devices in the market use auto-focus mode to do the focus job on the monitored scene, by which a focus motor that controls the focus status of the lens inside the monitoring device will selectively operate according to the current focus status of the scene and to change the focus length of the lens to acquire clear monitored images. However, it is a common case that some persons or objects of no interest may temporarily show up in the monitored scene, whose movements are the cause of frequent focusing of the monitoring device. As a result, the time of use of the focus motor increases, making the focus motor faster to age and the focus behavior will be overly interrupted by irrelevant events that there is highly chance to lose clear images of the monitored position/object.